Certain proteinaceous materials of a vegetative origin are known to contain appreciable levels of phytates and phytic acid. Vegetable proteins from corn, wheat, rice, soybeans, peanut meal, sesame meal, rape seed meal, cottonseeds, lima beans, navy beans, barley, oats and sunflower seeds have been reported as containing phytic acid and phytates. Although the phytates and phytic acid content in excess of 7% has been reported, the content for cereal and oil seeds typically ranges from about 1% to about 5%.
Phytates and phytic acid are known to have a deleterious effect upon the nutritional quality of foodstuffs. Phytates and phytic acid form metal-phytate and phytate-protein complexes. The metal-phytate complexes are reportedly responsible for dietary deficiencies of essential metals such as zinc, magnesium, manganese, calcium, copper, iron, etc.
Numerous techniques for removing phytates and phytic acid from proteinaceous materials have been reported. Morehouse et al. (U.S. Pat. No. 3,966,971) reports removing phytate by treating vegetable protein source materials with an acid-phytase. Generally, a portion of the phytates are unaffected by the phytase treatment. In a patent issuing to Iacobucci et al. (U.S. Pat. No. 3,736,147), there is disclosed a process for removing phytic acid by ultrafiltration at a pH 2.0-4.5 in the presence of a large excess of divalent cations, such as calcium and magnesium ions. Iacobucci et al. report that the stoichiometric displacement of the phytic acid from the soy proteins:phytic acid complex at pH 3.0 requires an excess of at least 70 equivalents of calcium ions per equivalent of charged basic group present in the protein. Goodnight, Jr. et al. (U.S. Pat. Nos. 4,072,670 and 3,995,071) report the preparation of soy protein isolates of a reduced phytic acid-phytate content by treating aqueous soy protein extracts at a pH 10.5 or higher to insolubilize phytates and phytic acid. The insoluble phytates and phytic acid components are separated from the soy protein extract to provide a low-phytate isolate. The treatment of soy proteins at a pH 10.0 or higher results in the formation of undesirable by-products which adversely affect the isolates nutritional quality.
Other patents have treated proteinaceous materials with metal hydroxides for purposes unrelated to phytate removal. U.S. Pat. No. 4,216,144 by Ashmead discloses the preparation of iron proteinates or chelates of iron from hydrolyzed vegetable proteinaceous materials. An early patent by C. Roehr (U.S. Pat. No. 820,824) discloses a method for separating proteins from fatty materials in proteinaceous materials by precipitating the protein with water-insoluble and alcohol-soluble metal hydroxides in alcohol such as the hydroxides of aluminum, copper, zinc, nickel, cobalt and silver. U.S. Pat. No. 4,212,799 issuing to C. Nuzzolo et al. discloses treating sunflower meals with aluminate ions at a pH 10.5 to complex certain polyphenolics and prevent their oxidation of quinones. Throughout the sunflower meal treatment the aluminum is maintained in solution. The aluminum is maintained in solution during the isoelectric precipitation of the sunflower proteins at pH 5.0 via water-soluble aluminum complexing agents such as citrate.
Unfortunately the phytate and phytic acid removal proposals provide an ineffective and uneconomical solution to the phytate and phytic acid problem. Processes relying upon pH 10.0 or higher produce undesirable by-products. The divalent metal addition processes substantially increase capital equipment, raw material and waste material disposal costs. The techniques required for phytate and phytic acid removal unduly complicate the manufacturing process and require extensive modification to existing manufacturing facilities and process.
In the manufacture of proteinaceous materials, the industry has long-sought a simple and direct method to alleviate problems associated with phytates and phytic acid. A manufacturing process which could be effectively and easily integrated into existing manufacturing facilities without requiring extensive processing and equipment alterations would provide definitive advantages. An economical and effective manufacturing process adapted to overcome the phytate and phytic acid complexing problems would also significantly enhance the nutritional value of vegetable proteins. A significant technological advance within the field of vegetable protein would arise by a system that relied upon an additive which facilitated the manufacture and enhanced the nutritional and functional efficacy of the protein product without requiring phytic acid or phytate removal.